Process and apparatus for congealing liquids



@QL @9 i938. E, THQM PSQN 2,132,364

PROCESS AND APPARATUS FOR GONGEALING LIQUIDS Filed NOV. 14, 1935ATTORNEWI plates I2 and I3.

means for enabling the attendant or operator to observe the ow of air. f

A further feature of the invention lies in the provision of apparatus ofthe aforementioned character including a device for feeding the mixessing of any fluid with a g'as.

4One of the features of the invention is the provision of an improvedmeans for more efficiently controlling the flow of air or gas to theliquid or iiuid into which the air or gas is int-roduced. v

Other features, objects and advantages of the present invention will inpart be pointed out and in part become apparent in connectionl with thefollowing description of certain detailed forms of apparatusillustrating the invention, reference being had to the accompanyingdrawing wherein:

Fig. 1 is a side elevation of apparatus in accordance with the presentinvention, shown partially in section; and

Fig. 2 is an elevation, partly in section, illustrating a detail of oneform of air feeding device,

also in accordance with the invention.

Referring now to the drawing, there is shown at I a container of anysuitable construction which may be generally cylindrical, lined withinsulating material II, and provided with end An inner wall I5 may serveto form an annular compartment I4, through which a refrigerant maycirculate, and may yalso serve y as the outer wall of a chamber VIthrough which the material to be refrigerated passes. The parts of theconstruction thus far described may-be composed of any materials whichare satisfactory for the purposes indicated. Extending through thechamber I'I, preferably horizontally, is a shaft I6 which may besupported in any suitable bearings carried by the end walls I2 and I3.This shaft may be driven from a source of power such as an electricmotor (not shown) and carries, as will hereafter be described, thevarious devices for feeding and mixing or stirring the materials-to becongealed or frozen. When a liquid refrigerant is employed, it may befed into the annular chamber I4 through an inlet pipe I8 and aftercirculating about may discharge through outletpipe I9. Ordinarily, therate of refrigeration may be controlled by adjusting the flow ofrefrigerant, for instance, by suitable valves (not shown), so that theproduct will be discharged at uniform temperature. However, other typesof refrigerant may be employed, or other arrangements made for effectingthis purpose.

The liquid mix to be fed to the refigerating chamber II may be suppliedthrough a pipe to a suitable reservoir 2I, under control of a valve 22actuated by float 23, for. affording a constant head of liquid. Asuitable liquid pump 25 is preferably used to force the mix into chamberI'I through a pipe 24, the end 26 of which is preferably locatedadjacent the inlet end I2 of the chamber I1. When it is desired to feedthe mass, consisting principally of milk, in the case of ice cream, andthe fruit, nuts or other avoring through a separate tube, the latter maybe introduced by means of a pump 28 through a pipe 2l, the outlet end ofwhich may also be located near the same end of the refrigeratingchamber. It will be appreciated, however, that when desired, the mix andflavoring may both be fed in at one point, and that while advantages aresecured by 10 introducing the liquid close to one end of the chamber, itmay be introduced at other points.

The air for the desired over-run may bc fed in through a pipe 30, by adevice hereafter described, also near the end of the chamber where theliquid l5 mass is introduced. In the form shown in Fig.

l, the air line 30 separately enters the chamber Ill, but if desired,the air may be mixed with the liquid prior to the time this liquidenters the refrigerating chamber. On the other hand, at 20 least in thebroader aspects of the invention, the air may be introduced into theliquid at `a point farther along the chamber I'I toward the outlet end,although it is advisable to introduce the air before the mass becomestoo solid. 25

Adjacent the inlet end'of the chamber I l, there is preferably mountedupon the shaft IB'a suit,- able spiral screw 3|, adapted to feedthematerial forward. 'In the form illustrated, this screw is solid and hasa diameter substantially the same 30 as the diameter o f the chamber I'Iso that it will efficiently feed the material forward, and also assistsomewhat in preventing pressure changesin the other end ofthe chamberI'I from being refluxed so as to affect the air fed through pipe 3B.This screw may have any suitable number of convolutions, butadvantageously occupies only a relatively small portion of the length ofthe chamber I1, Where such a screw is employed. it may be desirable toblock out certain portions of the'chamber I4 through which the coolingmedium circulates so that'the refrigeration will not result ininterfering with the operation of the screw. With this purpose in view,any suitable filling material may be inserted as at 32, or theconstruction maybe otherwise modified so that the refrigerant does notcirculate around the portion of the chamber in which the screw islocated. Between the screw 3I and the outlet v end I3 of the chamber,there may be provided, 50 for stirring or beating the mix and air, adasher indicated generally at '33.

This dasher may comprise a pair of radial members 34 carrying a seriesof longitudinal whipper rods 35. Propeller blades 36 may also 55 besecured to or formed on the shaft I6, while other blades 31 may extendat angles as shown, being mounted upon suitable rods 38. A rectangularframe 39 may be mounted on the shaft and have secured thereto scraperblades 4U which 60 may be secured through bolts 4I. If desired, theouter portions 42 of the scraper blades may be made of 'somewhatflexible material. While the form of dasher described is particularlyadvantageous for many purposes, and while claim may bemade to itelsewhere, it will be understood that the present invention in itsbroader aspects is not limited to any particular type of dasher, or,indeed, even to the use of adasher..

vice.

In order to provide for a uniform feed of air side becomes greater thanthe critical value of there is preferably provided means for maintaininga supply of air under substantially constant pressure and a device inthe air line which serves to prevent pressure changes or pulsations inthe freezing chamber from backing up or otherwise affecting the desiredthis chamber. In accordance with one preferred form of the invention,this device comprises a constriction in the air line, such as a standardorifice or short tube, which once calibrated lfor given conditions,requires no further adjustments and is automatic in operation.Preferably, the apparatus also includes avalve ofsuitable constructionfor admitting air or other gas from a high pressure reservoir, to achamber on the upstream side of the oridce or the like, and formaintaining any one of a number of dierent predetermined constantpressures in said up stream chamber, whereby various desired constantrates of feed of air may be secured.

With reference to the form of device illustrated, there may be employedan air supply tank or high pressure reservoir 50 connectedto the airline 3d. For instance, tanks of compressed air, carbon dioxide or othersuitable gas may be connected to the line, in multiple, if desired, andbe valved in or out as required, or a suitable air compressorl may beemployed for maintaining a uniform pressure in the tank 50. anyconvenient known equipment being used .to start the compressor when thepressure in tank 50 falls below a pre-set minimum and to stop l it whena pre-set maximum is reached. If desired, the air from tank 50 may bewashed and /or filtered through any satisfactory type of known device 52for this purpose.

The air is then passed through the manually operated pressure regulatingvalve 53, by which the air pressure in the upstream chamber re' ferredto may be set to the desired pressure for a given over-run. Thisregulating valve is preferably of such design that it can take the highpressure air from the air source 50 and reduce it to any desired lowerpressure by a setting of the manual control and maintain it at suchdesired pressure, regardless of variations in reservoir pressure, solong as this latter pressure re mains higher than the pressure for whichthe valve has been set. Such valves arein themselves known. Pressuregauges 55 and 56 may be attached to the line 30 on either side of thevalve 53, so that the operator can readily note vthe existing pressuresand make any necessary adjustments. Gauge E@ indicates the pressure inthe upstream cham er.

In accordance with t e preferred f orm of the present invention, thereis provided an orifice or the lille and a source of constant pressure socombined that there is a constant flow of air through the orifice orsimilar constriction regardless of changes oi pressure orA backward pul-.sations on the downstream side of the orifice. in

order to obtain this result to best advantage. it is preferred toconstruct the orifice, having regard to the desired rates of flow (themass of air to be delivered per unit of time), so that the absolutepressure on the downstream side of the orifice (is less than about .53.times the absolute pressure on the upstream a suhstantiallyrconstantvelocity and constant flow through the orifice. That is to say, thepressure on the upstream side'should be maintained, for a given orifice,so that it is more than rabout double theppressure onv the downstreamside, for when the pressure on the downstream constant ow of air intoside, which results in .53 times the pressure on the upstream side, theilow tends to vary from the desired constant rate. However, it will beappreciated that in some circumstances, Where maximum accuracy is notrequired, the practice of the invention, at least in its broaderaspects, is not confined to the critical value stated. Moreover, theconstant factor .varies for diierent gases, but can be determined forany particular gas. l

While I do not wish to be limited to the following analysis, it appearsthat by providing an orice or the like which is large enough to permitthe desired `mass of air per unit of time to flow through it,.and whichat the same time is small enough, as compared to the upstream chamber,to vprevent pressure changes or pulsations on the outlet or downstreamside of the orifice from substantially affecting the steady iiow of airthrough the orice at high velocity or the pressure on the upstream side,and by maintaining a relatively high pressure on the upstream side, thehigh velocity of the air passing through the orifice will maintain orwork to produce a constant ilow of air through the orifice, so that themass of air which is supplied to the downstream side, and thus the massof air which is delivered per unit of time, is a constant, irrespectiveof any ordinary changes oi' pressure or pulsations below the orifice, solong as the required absolute pressure differential on opposite sides ofthe orifice is maintained. l

The orifice may be regarded as a metering orifice, and so long as gas issupplied at constant pressure on the lip-stream side of the meteringorifice and is maintained at more than about twice the pressure of gason the down-stream of the orifice, the fiow oi gas and' the mass thereofthrough the4 metering orice will be constant in spite of any backpressures on the down-stream side of the orifice due to pulsations orfluctuations. Usually such fluctuations or pulsations in pressure onfthe down-stream side of the orifice are caused by the action in thefreezer, be that action due to the operation of the dasher or theimproper operation of the outlet valve. This metering orifice preventsthe pulsations or uctuations from reachingthe pressure-reducing valve53,and thereby prevents any adverse effect in delivering a constant massof gas for use in the .freezing oi' the ice crearu.` That is to say,none of the pulsations or fluctuations which normally develop in thefreezing oi the ice cream, are permitted to adect in any manner theproper supply of air. The orifice prevents pulsations from reaching thepressure reducing valve lit to affect its function of delivering aconstant pressure of gas at the upstream side of the orice.

an example oi a ratio which-has been found to be satisfactory is wherethere is a 30 lb. per sq. inch'pressure on the up-stream side of themeteringorifice t0, and a pressure on the down-stream side ofthe orificevarying between 2 and d lbs. per sq. in., giving a momentary pressure of3 lbs. per sq. in.. If the 3 lbs. per sq. in. is divided by 30 lbs. persq. in., it will be noted that the ratio is .1, and is therefore lessthan the .53 figure noted toA the critical pressure the mass of airowing.

through the orice increases though it continues to ow at the criticalvelocity.

The air control for this type of machine is intended to control the massof air supplied to the freezer rather than the pressure at which itA issupplied. The mass of the mix supplied `to the freezer is controlled bycommon methods. For the purpose of controlling the percentage of overrunit is necessary to control accurately the mass of air supplied to thefreezer.

When the ratio of pressures below and above the orifice' 60 ismaintained at or less than the critical value of .53, the mass of airflowing through the control is in direct proportion of the pressureabove the orifice, and changes in pressure on the down-stream side. ofthe orifice will not affect the flow of air unless said pressure willchange the ratio to more than .53. This feature isl of advantage insimplifying the manufacture, calibration and operation of the machine.

Of course, if the valve 45 in the outlet pipe M wereclosed the pressurein the freezer would soon build up until the back pressure below or onthe down-stream side of the orifice would become greater than .53 timesthe pressure above the orifice, but in normal operation the valve 45 isopen so that the frozen material may flow out of the machine. Underthese conditions the total back pressure will not build up and onlymomentary fiuctuations in pressure or pulsations have to be provided forso as not to reduce the mass of air inflow to the down-stream side ofthe orifice. It will. be understood that usually the valve 45 is open toallow continuous outiiow of the ice cream, but intermittent operation ofthis valve 45 is possible so long as it does not remain closed for toolong a period or for such a length of time that the pressures in thefreezer and supply line will build up to a point above the critical'ratio figure of .58.

1f for any reason, the mass of air supplied changes and there is novchange in the mass of mixsupplied then the percentage of overrun willchange, thereby changing the quality and unisures cannot affect the massof air supplied, and' therefore the quality and uniformity of the icecream will be maintained. By reason of the use herein of the meteringorice under the conditions designed for it the quality of the ice creamproduced is always maintained and uniformity is accurately controlled.

Moreover, by providing for the maintenance of a constant pressure abovethe orice at any one of various different values, and by providing a re-A stricted opening of the character described, through which the air owsfrom a relatively high pressure to a relatively low pressure, the flowof air through the constricted opening may thus be maintained at any oneof a number of different constant rates substantially irrespective ofthe pressure on the downstream side so long as this pressure does notfluctuate too greatly above the critical value mentioned.

Thus, there is provided a construction which is particularly effectivefor feeding air or gas at theconstant rate especially desired in thecase of congealed liquids which should contain a uniform over-run of airor other gas. Moreover', the construction is especially simple tomanufacture and easy to operate, since once the operator has set thecontrol valve for a predetermined upstream pressure, the feed of airwill be continuous and constant without any further supervision, as longas the upstream pressure is maintained, as it can be through anyconvenient device.

As shown diagrammatically in Fig. 2, the constriction in line 30 maycomprise a member such as a plate 6| carrying a standard orifice 60 orshort tube preferably constructed so that the pressure in downstreamchamber 63 is less than about .53 times the pressure in the upstreamchamber 62 (for air). Under normal operating conditions the upstreampressure will be sufficiently high to maintain this pressure ratio.

.'I'he diameters of the chambers should be large with respect to thediameter of the orifice, usually at least 5 to 1. The orifice may be ofany common type such as sharp edge, rounded edge, thick plate, or shorttube, or may be of a somewhat modified form. While an orifice isgenerally preferred, a properly proportioned throat, such as a Venturithroat may likewise serve present purposes, though not as accurate.Where the term orifice-type is used herein it intends any suitableorifice or equivalent construction.

The constriction in the pipe 30 may be located at any convenient pointtherein, but ispreferably not immediately adjacent the end of the pipewhere the air enters the refrigerating compartment, so that there is asubstantial volume of air between the orifice and the point where theair enters the mix. However, in the broader aspects of the device,theparticular location of the constriction is not of the essence.

In order to enable the operator to note the flow of air, and thus makedoubly sure of desired conditions, :a visible flow meter 51 may beattached to line 30 at any convenient point,. advantageously betweenorifice 60 and the cham.-

ber i1, so that the air flow may be observed. To one familiar with theoperation of a particular machine, this device alone may furnish anapproximate, if not exact, indication of the air flow, and it may evenbe possible, when such a meter is used, to dispense with one or more ofthe other gauges.

While the description has been largely confined to the introduction ofair into mix during the manufacture of ice cream, it will be appreciatedthat the present apparatus is also useful in connection with introducingother compressible gases into various non-compressible liquids which arecongealed into solids owing to a temperature change, especially whereverthere is change in volume during the operations, and wherever anintimate and uniform mixing is desired. For

iii

' volume of the final product.

. in a change in the cubic inchy flow of such other operations it may bedesirable to construct the orifice or the like so that the pipe sectionin which it lies is readily removable, and this and other details of thearrangement of the orifice may take any convenient form.

The air or gas flow system may be employed for other purposes ifdesired; whether the air is to flow to materials which are later to be'congealed. or' to flow into a mixture of liquids and gases, or even intogases aionewhere constant flow is an object.

This apparatus provides for the addition of a desired amount of volumeof air` to the total Also the appa--4 ratus may be employed forother'purposes than making ice cream and with or without' refrigeration,or with only a small amount of refrigeration. In the event the apparatusis `employed where it is desirable at times to employ heat "instead ofchilling, it will be found that it is readily adapted for such purposes.Some of= the examples of such other ,uses constitute thepreperation oflard, cold cream, cotton-seed oil; honey with air distributed thereinand the like, or any y other material that needs air or gas distributedtherethrough. This improved apparatus also may be readily employed inthe hydrogenation of various products.

It will be noted from the description herein that av definite size areaof orice will permit, under a definite pressure, a flow of a certain`amount of cubicdnches of air orgas per minute. Changing the pressurewith the same area of orince will give a different cubic inch flow ofairper minute, or changing the' area of the orifice will give anotherchange inv volumetriciiow of air or gas. In addition, the use of anothergas with even the same larea of orifice, will result gas. It will thusbenoted that, once the desired orifice is employed and the properadjustment made, the percentage of over-run will be maintained withinlimits that allow the production of ice cream that is very acceptable tothe market.

It will further be noted thatgthe air or gas is fed continuously and ata substantially con` stant volumetric rate. The feeding of the air orgas to the freezer is, therefore, not intermittent. As indicated in thedetailed description above, there is provided an improved apparatus inwhich the liquid and gas are continuously admitted in substantiallyconstant stream or streams to the chamber in which the mixing, or mixingand freezing take place. It will, therefore, be seen that the improvedapparatus herein, in producing ice cream, may be said to congeal aliquid or a'liquid. mix while incorporating thereinto air or a gas. Theapparatus also controls the volume of air or gas per unit of timetherebyproviding the desired amount of air volume tov the total volumeof the final product. The percentage of thisadded air volume to thevolume of the final product is known as the over-run.

The present invention thus provides a construction which is reasonablysimple and inexpensive to manufacture and which enables air to be fedinto a chamber in which it is mixed with a liquid and congealed. The airis fed at a uniform rate without the needfor any moving parts in the airfeeding device. `Moreover, the present construction enables an unskilledoperator to readily manipulate the mechanism so as to produce a riesiredfeed of air and maintain the same `once the adjustments have been made.

Furthermore, the operator can at all times note the rate at which air isbeing fed and thus easily supervise operations. The construction,especially in the preferred form, is highly emcient in eliminating thereiiuxing of pulsations or pressure changes in the refrigeratingcompartment in a manner which will not interfere with the constant andcontrolled rate of feed ofthe air. The constriction in the air feed lineaffords an especially satisfactory and, at the same time, simple mannerof controlling the air feed at the proper rate and uniform pressure.Moreover, there are no moving parts to get out of order, and a singleorifice may he employed for diuerent desired rates of new of gas.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no desire, in the use ofsuch terms and expressions, of excluding any equivalents of the featuresshown and described, or portions thereof, but it is recognized thatvarious modifications are possible within the scope of the inventionclaimed.

I claim: y i. in continuous apparatus for congealing liquids andsimultaneously mixing gas therewith,

' a cylindrical chamber, a rotatable shaft extendat constant rates, theow of the gas being independent of a rate of dow of the liquid means tocontinuously withdraw congealed product, and a 'screw feeding membercarried by said shaft adjacent the points of admitting liquid and gas.

2. In continuous apparatus for congealing liquids and simultaneouslymixing gas therewith, a cylindrical chamber, a rotatable shaft extendinglongitudinally thereof, stirring means carried by said shaft, means tocontinuously admit in constant streams liquid and gas to said chamber atconstant rates, means to continuously withdraw congealed product, and ascrew feeding member carried by said shaft adjacent the points ofadmitting liquid and gas, said. screw comprising a solid bladelconstructed and arranged to extend across substantially the fullcross-sectional area of said chamber, and said gas ad-v mitting meansbeing adapted to feed the gas-into the chamber at a point on theopposite side of said blade from said stirring means.

3. An apparatus for continuously mixing a gas with liquids andsimultaneously congealing said v liquids, a refrigerated chamber, meansfor feeding liquids' to said chamber at a predetermined rate, a supplyof gas under super-atmospheric pressure', means for continuously feedingsaid gas from said supply to said chamber at a constant rate of flow forbeing mixed into said liquids, said means including a conduit having aconstricting member mounted therein and having said member provided witha small unobstructed orifice, and means within said chamber for movingsaid liquids and the gas occluded therein from one end of said chamberto the other end thereof as the congealing of the body of liquids andgas takes place.

4. In a freezerfor making ice cream continu ously, a 'refrigeratedchamber, means for feeding an ice cream mix into said chamber, a supplyof gas under super-atmospheric pressure, a conduit connecting said gassupply to said chamber, and means mounted in said conduit comprising aconstricting member provided with afs'mall unpressure to pass to saidchamber continuously and at a substantially constant volumetric rate ofiow, and a moving dasher mounted within said chamber and adapted tocooperate with said chamber for whipping the ice cream mix and fortranslating the same through said chamber as the mix is being congealed.

5. In a freezer for making ice cream continuously, a refrigeratedchamber, means for feeding an ice cream mix into said chamber, a supplyof gas undersuper-atmospheric pressure, a. conduit l connecting said gassupply to said chamber, and

means mounted in said conduit comprising a constricting member providedwith a small unobstructed orice which allows the gas under pressure topass to said chamber continuously and at a substantially constantvolumetric rate of ilow, said constricting member acting to keep thepressure of the gas on the up-stream side of said member above thecritical pressure for said orifice, and a dasher mounted within saidchamber and adapted to cooperate with said chamber for whipping the icecream and for translating the same through said chamber as the mix isbeing congealed.

6. An apparatus of the character described for congealing liquids andmixing gas therewith, a gas-feeding device comprising a container forthe gas under super-atmospheric pressure, a mixing chamber for saidliquids and said gas, a conduit leading from said container to saidchamber, and means comprising a constricting member provided with asmall unobstructed orifice, said member being interposed in said conduitand constructed and arranged to control the mass of delivered gas andmaintain a continuous substantial volumetric rate of flow through saidorifice to said chamber under set operating conditions.

7. In an apparatus of the character described for congealing liquids andmixing gas therewith, a mixing chamber, a gas-feeding device comprisinga container for gas under super-atmospheric pressure, a conduit leadingfrom said container to said mixing chamber, and means comprising aconstricting member provided with a smallunobstructed orifice, saidmember being interposed in said conduit at a substantial distance fromsaid mixing lchamber and constructed lto control the mass of deliveredgas and maintain a continuously substantial volumetric rate of fiow ofgas to said mixing chamber.

' 8. In apparatus of the character described, in combination, a gasfeeding device comprising a source 'of lgas under constantsuper-atmospheric pressure, a conduit, means comprising a constrictingmember provided with a small unobstructed orifice interposed in saidconduit and constructed and arranged to maintain a sub- 1 eratingconditions of less than about .53 times the pressure on the feed side.

10. Apparatus as claimed in claim 6, wherein a visible flow meter isinterposed in said line.

11. Apparatus for congealing liquids, comprising in combination, amixing and congealing chamber, means in said chamber causingbackpressure pulsations. a fluid feed line to said chamber, means forsupplying iiuid at constant pressure to said feed line, and aconstricting member in said feed line provided with a very small openingtherein through which said iluid must pass at a velocity equal to themaximum or critical velocity for said fluid through said oriilce andsuillcient to prevent normal pressure pulsations in said feed line onthe discharge side of said restricting member from 'affecting the fluidpressure in said feed line on the fluid supply side of said opening,thereby preventing substantial variations in the continuous rate of flowof said fluid through said opening While the fluid pressure ismaintained.

12. An apparatus of the character described for congealing liquids andmixing gas therewith in combination, a gas-feeding device comprising asource of gas under superatmospheric pressure, a mixing chamber to whichthe liquids and the gas are conducted, a conduit leading from thegas-feeding device to said chamber, means comprising a constrictingmember provided with a small unobstructed orifice, said member beinginterposed in said conduit, said member being constructed to maintain acontinuously substantial volumetric flow of gas to said mixing cham'-ber, and a manually adjustable pressure-reducing valve interposed insaid conduit between the source of said gas and said constricting memberfor maintaining a constant pressure in said conu duit adjacent theup-stream side of said constricting member.

13. In the apparatus for continuously congealing liquids While at thesame time incorporating a gas therein, a chamber, means to feed to saidchamber at a substantially constant rate the liquid to be congealed, asupply of gas to be added to the liquid, means for introducing said gasto said chamber continuously and at a sub'- stantially constantvolumetric rate of flow and independent of the rate of ow of the liquid.

14. In an apparatus for continuously producing ice cream, thecombination of a chamber, a refrigerant for cooling said chamber, asupply of ice cream mix, means for feeding said mix to said Vchamber ata substantially constant rate of iiow, a supply of air to be added tothe mix at a pressure greater than atmospheric pressure, and means forgoverning the rate of flow of said air to said chamber so as to supplythe air continuously and at aV substantially constant volumetric rate tothereby maintain the volume of said air to the volume of said mix at asubstantially .constant ratio and thereby obtaining a desired amount ofair volume in the final product.

15. In an apparatus for continuously producingice cream, the combinationof a chamber, a refrigerant passage around said chamber, a supply of icecream mix, means for feeding said mix to said chamber at a substantiallyconstant rate offlow, a supply of air to be added to the mix at apressure greater than atmospheric pressure, means for governing the rateof flow of said air to said chamber so as to supply the air continuouslyand at a substantially constant volumetric rate to therebymaintain theVolume of said air to the volume of said mix at a substantially constantratio and thereby obtaining a desired amount of air volume in the finalproduct, and means for agitating the mix as it passes through saidchamber and as it absorbs the air and becomes congealed. y

16. In the process of making ice cream continuously, the steps offlowing an ice cream mix into a refrigerated chamber at a continuousrate,

flowing air at a pressure greater than atmospheric away from said mixingchamber and being propressure into the same chamber continuously and at'a substantially constant rate ot flow. mixing the air into the icecream mix as the mix is being congealed, and withdrawing the ice creamfrom said chamber.

17. In the process of making ice cream continuously, the steps offeeding an ice cream mix continuously and at a substantially constantrate into a chamber, feeding air at a pressure greater than atmosphericpressure continuously into said chamber and ata substantially constantvoluf metric rate of flow, cooling said chamber. beating the air intothe ice cream mix to give a substantially uniform distribution o! theair therethrough while congealing the mixture'. and allowing the icecream to issue from said chamber.

18. In the process of occluding a gas in a liquid. the steps ofsupplying a liquid continuously at a substantially constant rate to amixing chamber, producing asubstantially constant volumetric rate ofiiow'of the gas independent of the rate of flow or the liquid andfeeding the same continuously to said mixing chamber, agitating saidliquidand said gas to distribute said gas substantially uniformlythroughout said liquid during the moving'of said liquid with the gasthrough said mixing chamber, and allowing said mixture with the occludedgas therein to issue from said chamber substantially continuous.

19. In a gas flow system in an apparatus of the character described andbeing capable ot being operated at various predetermined pressures, thecombination of a condultior conducting the gas. means for supplying thegas under a predetermined constant super-atmospheric pressure to saidconduit. a mixing chamber. means in said mixing chamber causingpulsations in said conduit adjacent said mixing chamber.

o a constricting` member mounted in said conduit vided with a relativelysmall opening therein through which said gas must pass at a velocityequal to the maximum or critical velocity for said gas through saidorifice and sufiicient to prevent normal pressure pulsations in the partof said conduit between said mixing chamber `and said constrictingmember from affecting the said gas pressure in said conduit on the gassupply side of said constrlcting member, thereby preventing substantialvariations in the continuous rate of flow of said gas through saidorince while the gas supply pressure is maintained.

20. In apparatus of the character described, in combination, a conduitfor conducting gas, means to supply`gas under constant super-atmosphericpressure to said conduit, means to reduce said pressure to any one of anumber of substantially constant pressures in said conduit, a mixingchamber. means in said mixing chamber causing pulsations in said conduitadjacent to said mixing chamber, a constricting member mounted in saidconduit between said reducing means and said mixing chamber, saidconstricting member being provided with a small opening adapted tomaintain a constant velocity of the gas under the selected pressure.said orice being constructed and said pressure being adjusted to preventnormal pressure pulsations in said conduit near said mixing chamber fromaffecting the pressure between said constricting member and'said reduceing means whereby a substantially constant ow oi the gas is maintained.

21. A combination as claimed in claim 19 wherein said constrictingmember is formed as a iiat plate mounted across said conduit and saidopening isof less than about one twenty-mth of the cross sectional areaof the conduit.

` EMERY THOMPSON.

